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The current study examined whether persons with a history of mTBI exhibited greater cognitive decline in response to physiological arousal than healthy controls. It was hypothesized that individuals with a recent history of mTBI would demonstrate poorer cognitive functioning at simulated high altitude than persons without such a history, and that sex and physical activity levels would moderate this relationship. Participants with a history of mTBI (n = 20) and never-injured controls (n = 28) completed two cognitive testing sessions using the NIH Toolbox Cognitive Battery: one at mean sea level, and one in a normobaric hypoxia chamber. Attention and executive functioning composite scores were created. Participants also completed questionnaires about their concussion history and affective change and altitude sickness symptoms.A mixed-model repeated measures MANOVA found a main effect of condition such that participants demonstrated improvements from sea level to simulated altitude (Wilk’s Lambda = 0.23; F(2, 43) = 72.87, p < .001; ηp2 = 0.77) for both attention (F(1) = 109.34; p < 0.001; ηp2 = 0.71) and executive functioning (F(1) = 30.16; p < 0.001; ηp2 = 0.41) scores. There was also an effect of concussion history on cognitive test performance overall (Wilk’s Lambda = 0.85; F(2, 43) = 3.94; p < 0.05; ηp2 = 0.16), though univariate analyses were nonsignificant when considering attention (F(1) = 1.71; p = 0.20; ηp2 = 0.04) and executive functioning (F(1) = 0.67; p = 0.42; ηp2 = 0.02) independently. Univariate interactions were observed between condition and gender on the attention composite score (F(1) = 4.51; p < 0.05; ηp2 = 0.09), such that males exhibited greater improvement from sea level to simulated altitude than did females, and among condition, group, and gender on executive functioning (F(1) = 4.58; p < 0.05; ηp2 = 0.09), such that female participants with a history of concussion experienced the least improvement from sea level to simulated altitude. Exploratory analyses found that individuals with a history of concussion experienced greater affective change than individuals without a history of concussion over time at simulated altitude (Pillai’s Trace = 0.16; F(2, 44) = 4.03; p < 0.05; ηp2 = 0.16). A univariate interaction effect among condition, concussion history, and total mood disturbance score on attention composite scores (F(1) = 11.40; p < 0.01; ηp2 = 0.21), indicated that, within the high affective change group, control participants exhibited significantly greater improvement across testing conditions than did concussion participants.Overall, this study serves as preliminary evidence for the role of stress as a modifier of cognitive functioning and affective experience after an apparently resolved concussion long after the time period that clinicians typically consider as normative for such a relationship to exist. As significant practice effects complicate these results, future research should employ alternative methodology to account for (or mitigate the impact of) practice effects and clarify the observed relationships. Should the present findings be replicated, they may present significant implications for future research and treatment at the intersection of mTBI and stress. |
